Impact of chronic obstructive pulmonary disease on exercise ventilatory efficiency in heart failure

Background: Heart failure (HF) and chronic obstructive pulmonary disease (COPD) coexistence increases morbidity and mortality. The intercept of ventilation (VEint) on the VE vs. carbon dioxide production (VCO2) relationship during exercise has been found to vary in proportion with dead space (VD) in HF. Considering that increased VD is the key pathophysiological abnormality in COPD but a secondary finding in HF we hypothesized that a high VEint would be useful in suggesting COPD as HF co-morbidity. Our aim was to assess whether an elevated VEint suggests the presence of COPD in HF. Methods: In a multicenter retrospective study, the VE-VCO2 relationship was analyzed both as slope and intercept in HF (n = 108), HF-COPD (n = 106) and COPD (n = 95). Patients with pulmonary arterial hypertension (PAH) (n = 85) and healthy subjects (HF) (n = 56) served as positive and negative controls relative to VE-VCO2 abnormalities, respectively. Results: Slope and VEint varied in opposite directions in all groups (p < 0.05) being VE-VCO2 slope highest and lowest in PAH and healthy subjects, respectively. No slope differences were observed among HF, HF-COPD and COPD (32 ± 7, 31 ± 7, and 31 ± 6, respectively). VEint was higher in HF-COPD and COPD compared to HF, PAH and controls (4.8 ± 2.4 L/min, 5.9 ± 3.0 L/min, 3.0 ±2.6 L/min, 2.3 ± 3.3 L/min and 3.9 ±2.5 L/min, respectively; p < 0.01). A VEint >=4.07 L/min identified patients with high probability of having COPD or HF-COPD (sensitivity of 71.6% and specificity of 72.0%). Conclusion: These data provide novel evidence that a high VEint (>=4.07 L/min) should be valued to suggest coexistent COPD in HF patients.